Synthetic jet air freshener

Abstract

An air freshening device comprises a housing defining a chamber. The chamber contains air and a supply of fragrance material that scents the air inside the chamber. A mechanical oscillator is in fluid communication with the air in the chamber and is configured to transmit acoustic waves in the chamber. A narrow conduit provides a passage from an interior of the chamber to the atmosphere outside the chamber. The conduit is dimensionally configured such that a synthetic jet from the narrow conduit is generated upon activation of the mechanical oscillator, the synthetic jet ejecting scented air from the chamber interior to the atmosphere outside the chamber. The mechanical oscillator may be driven intermittently, resulting in a consistent intensity and character of the emitted scent over the life of the product.

1 . An air freshening device, comprising:
 a housing defining a chamber, the chamber containing air and a supply of fragrance material that scents the air inside the chamber;   a mechanical oscillator in fluid communication with the air in the chamber and configured to generate acoustic pressure in the chamber at a selected frequency; and   a narrow conduit providing a passage from an interior of the chamber to the atmosphere outside the chamber, wherein the conduit is dimensionally configured such that a synthetic jet from the narrow conduit is generated upon activation of the mechanical oscillator, the synthetic jet ejecting a jet of scented air from the chamber interior to the atmosphere outside the chamber.   
   
   
       2 . The air freshening device of  claim 1 , wherein the narrow conduit is configured to hinder diffusion of the fragrance material from the chamber during periods when the air freshening device is not ejecting a synthetic jet. 
   
   
       3 . The air freshening device of  claim 1 , further comprising a control circuit that intermittently switches the mechanical oscillator on, and switches the mechanical oscillator off between periods when the mechanical oscillator is on. 
   
   
       4 . The air freshening device of  claim 3 , wherein the fragrance material scents the air inside the chamber by diffusion from the supply of fragrance material, and wherein periods of non-operation of the mechanical oscillator are selected to be sufficiently long for the fragrance material to substantially fully scent the air in the chamber before the oscillator again oscillates. 
   
   
       5 . The air freshening device of  claim 1 , wherein the selected frequency is substantially a natural frequency of the mechanical oscillator. 
   
   
       6 . The air freshening device of  claim 1 , wherein the selected frequency is substantially a Helmholtz resonance frequency of the chamber. 
   
   
       7 . The air freshening device of  claim 1 , wherein the mechanical oscillator comprises a voice coil actuator driven by an electric frequency generator source. 
   
   
       8 . The air freshening device of  claim 1 , wherein the mechanical oscillator comprises an electromagnetic actuator driven by an electric frequency generator source. 
   
   
       9 . The air freshening device of  claim 1 , wherein the mechanical oscillator comprises a passive mechanical system that vibrates in response to motions imparted externally to the air freshening device, and wherein the air freshening device is mounted in a motor vehicle, and the motions imparted externally to the air freshening device are imparted by the motor vehicle 
   
   
       10 . The air freshening device of  claim 1 , further comprising a wick in fluid communication with a reservoir of fragrance material. 
   
   
       11 . The air freshening device of  claim 1 , wherein further comprising a replaceable strip that holds the fragrance material. 
   
   
       12 . The air freshening device of  claim 1 , further comprising at least one additional conduit, each additional conduit providing an additional passage from the interior of the chamber to the atmosphere outside the chamber, wherein each conduit is dimensionally configured such that a synthetic jet from each conduit is generated upon activation of the mechanical oscillator, each synthetic jet ejecting scented air from the chamber interior to the atmosphere outside the chamber. 
   
   
       13 . The air freshening device of  claim 1 , comprising two flow fields, wherein the first field is inside the chamber near the mechanical oscillator and is a substantially acoustic non-flowing field, and the second field is near the opening of the conduit and defines a flow field which produces a jet flow. 
   
   
       14 . The air freshening device of  claim 1 , wherein the synthetic jet comprises a stream of air which flows through the nozzle in two directions, wherein the first direction is from the chamber to the atmosphere and the second direction is from the atmosphere to the chamber. 
   
   
       15 . An odor absorbing device, comprising:
 a housing defining a chamber, the chamber containing air and a supply of an odor-absorbing material that absorbs odors from the air inside the chamber;   a mechanical oscillator in fluid communication with the air in the chamber and configured to transmit acoustic waves in the chamber; and   a narrow conduit providing a passage from an interior of the chamber to the atmosphere outside the chamber, wherein the conduit is dimensionally configured such that a synthetic jet from the narrow conduit is generated upon activation of the mechanical oscillator, the synthetic jet ejecting substantially odorless air from the chamber interior to the atmosphere outside the chamber.   
   
   
       16 . A method of freshening air, the method comprising:
 providing a housing that defines a chamber, the chamber containing air and a supply of fragrance material that scents the air inside the chamber, wherein the housing includes a narrow conduit providing a passage from an interior of the chamber to the atmosphere outside the chamber, wherein the conduit is dimensionally configured such that a synthetic jet from the narrow conduit is generated upon activation of the mechanical oscillator, the synthetic jet ejecting scented air from the chamber interior to the atmosphere outside the chamber;   providing a mechanical oscillator in fluid communication with the air in the chamber and configured to transmit pressure in the chamber at a selected frequency; and   oscillating the mechanical oscillator.   
   
   
       17 . An actuator configured to dispense jets of scented air, the actuator comprising:
 a cavity storing an air freshening material therein, the cavity further comprising a narrow conduit that provides a passageway from an interior of the cavity to the atmosphere surrounding the actuator; and   a transducer configured to generate sound pressure within the chamber at a selected frequency, thereby causing a jet of scented air to flow from the narrow conduit;   wherein the jet is a synthetic jet.   
   
   
       18 . An air freshening device, comprising a narrow nozzle through which a jet of scented air is dispensed from a chamber to the atmosphere outside the chamber, wherein air is received from the atmosphere into the chamber through the same narrow nozzle to replace the scented air dispensed from the chamber, and wherein the jet is a synthetic jet. 
   
   
       19 . The air freshening device of  claim 18 , wherein the narrow nozzle is configured to hinder diffusion of fragrance material from the chamber to the atmosphere when the synthetic jet is not being dispensed. 
   
   
       20 . The air freshening device of  claim 19 , wherein the nozzle has a diameter of less than 2 millimeters. 
   
   
       21 . The air freshening device of  claim 19 , wherein the nozzle has a diameter of less than 1 millimeter. 
   
   
       22 . An air freshening device, comprising:
 a nozzle for cyclically ejecting scented air from a chamber to the surrounding space and receiving air from the surrounding space into the chamber, wherein the nozzle is dimensionally configured to produce a synthetic jet and to limit diffusion of fragrance material from the chamber when the synthetic jet is not being produced.